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to 500 ppm. These higher concen-
trations also caused some killing o f
Control of the Corn Earworm
small shoots, particularly in the on Sweet Corn in Southern California
tops of trees. However, little leaf G. G . Kennedy H. N. Nakakihara E. R. Oatman
drop was observed in these tests.
Some fruit on treated trees began to
darken and shrivel within about
ten days after ethephon applica- reduced level of infestation has
tion. apparently continued through 1974.
Additional studies conducted in Similarly, a reduction in the level
1973 and 1974 indicated that 250 of tomato fruitworm (= corn ear-
ppm was the maximum concentra- worm) infestations in processing
tion that could be used on Royal tomatoes occurred in Orange Coun-
Ann cherries in California because ty in recent years. There, the level
of gumming from treated trees. of fruitworm-infested tomatoes in
Even at this concentration, howev- untreated plots averaged 5.3 per-
er, serious gumming can occur in cent between 1969 and 1972
some seasons. A concentration of whereas, between 1973 and 1974, it
125 ppm h a s not produced serious averaged only 0.7 percent. Under
gumming but loosening at 125 ppm conditions of low earworm infesta-
has been inconsistent. Hence, there tions, satisfactory contro1 may be
appears to be seasonal variability obtained by insecticides that do not
in the response of sweet cherry provide acceptable control under
trees and fruit to this material. the pressures of a severe infesta-
Limited trials with ethephon tion.
were conducted on the fresh ship- During 1974, four commercially
ping varieties, Bing and Van, dur- available insecticides and three ex-
ing the 1972, 1973, and 1974 Larva of corn earworm feeding on kernels of
sweet corn. perimental compounds were evalu-
seasons. Ethephon at 250 ppm gave ated for control of the corn ear-
adequate loosening with no adverse T H E CORN EARWORM, He- worm on sweet corn in Riverside,
effects on fruit color, soluble solids riothis zea (Boddie), also known as where late-season corn earworm
or weight. In the tests with Bing he tomato fruitworm and cotton infestations continue to reach high
and Van, no serious phytotoxic ~ollworm, is a serious pest on levels. The commercial materials
effects were noted. weet corn, tomato, cotton, and were also evaluated for effective-
While ethephon can greatly aid ;everal other row crops grown ness in controlling the aphid Rho-
in fruit removal, the potential phy- :ommercialIy in California. Sweet palosiphum padi &.). This aphid is
totoxic effects of this material on :orn, however, is the preferred host usually not a serious problem on
sweet cherry trees in California tnd, although the Iarvae also feed sweet corn, but it occasionally
appear to outweigh its fruit loos- in the tassel in the whorl, the most develops high populations which
ening advantage. The use of ethe- iignificant damage results from are capable of devitalizing their
phon on cherries is not recom- ‘eeding on kernels in the develop- host plant. Additionally, it pro-
mended b y t h e University of ng ear. duces copious quantities of sticky
California and because of its phy- In the past, corn earworm infes- honeydew which foster the growth
totoxic effects, this material is not ations in southern California were of a black sooty mold which inter-
labeled for use on sweet cherries in io severe that virtually all ears not feres with normal photosynthesis
California. reated with insecticide were dam- and discolors the husk of the ears.
tged by this pest. For example, in All insecticides tested were ap-
he absence of insecticides, an plied to ‘Golden Cross Bantam’ (t
W. C. Micke is Extension Pomol- iverage of 99.1 per cent of harvest- strain) sweet corn planted June 17,
ogist, U. C. Davis; W. R. Schreader :d ears from successive plantings 1974, at the University of Califor-
is University o f California Farm n Orange County during 1963, nia’s Citrus Research Center and
Advisor, San Joaquin County; and !964, and 1965 were injured by the Agricultural Experiment Station.
J. T. Yeager and E. J. Roncoroni .ern earworm. In the Coachella Applications were made with a
are Extension Staff Research Asso- Jalley of Riverside County, be- high-clearance ground sprayer,
ciates, U. C. Davis. The authors ween 1966 and 1968, an average of equipped with four D-4 hollow-
gratefully acknowledge Amchem 39.0 percent of all untreated ears cone nozzles per row. Fifty gallons
Products, Inc., for supplying the iarvested during June were injured of spray mix per acre were applied
ethephon used in this study and for )y the corn earworm. More recent- at 90 to 100 psi. All treatments
the technical assistance of its repre- y, however, earworm damage has were replicated four times in a
sentatives Ken Dunster and Sheron )een considerably less severe in randomized complete-block design.
Christensen. The following grow- he Coachella Valley. Between The commercially available com-
ers also assisted in these studies: -969 and 1972, for example, only 9 pounds, lorsban (not presently ap-
Mario Podesta, Caminata and Po- )ercent of t h e untreated ears proved for control of corn earworm
desta, Lagomarsino Bros., and Rob- harvested during June were infest- on sweet corn), Lannate, Sevimol
ert Russell. d
b by the corn earworm. This and Gardona were appIied to plots
4 CALIFORNIA AGRICULTURE, AUGUST, 1975
235 ft. x 4 rows (40-inch spacing) phate), and UC 49035 (a carba- The present studies indicate that
at the rates shown in table 1. mate) were evaluated in a separate under conditions of a moderate
Presilk applications were made on test in which the plots were 50 ft. x corn earworm infestation, Lannate,
August 2 and 5; remaining applica- 3 rows. These materials were ap- Gardona, and Lorsban provide ef-
tions on August 7, 9, 11, 13, 15, 17, plied on August 7, 9, 11, 13, 15, 17, fective earworm control, while Sev-
19, and 21. On August 27 and 28, 19, and 21. On August 29-30, imol does not. The experimental
fifty ears were harvested per plot twenty-five ears per plot (100 per compounds tested showed suffi-
(200 per treatment) and individual- treatment) were harvested and ex- cient promise to warrant additional
ly examined for corn earworm dam- amined individually for corn ear- testing.
age and the presence of aphids. worm damage. The results are
Lannate, Lorsban, and Gardona presented in table 2.
provided effective control of the Although FMC 33297 and RH
corn earworm in the presence of an 218 at 1 Ib. appeared to give
infestation that produced 78 per- slightly better control than UC- G. G. Kennedy is Assistant Pro-
cent worm-infested ears in the 49035 and RH 218 at 0.5 Ib., there fessor and Assistant Entomologist;
untreated plots (table 1). In the were no significant differences be- H. N . Nakakihara is Staff Research
presence of this moderate level of tween the mean percentages of Associate IV; and E. R. Oatman is
infestation, Sevimol at 3 Ibs. actual infested ears in these treatments. Professor and Entomologist, De-
toxicant per acre did not provide All treatments had significantly partment of Entomology, Universi-
acceptable control. The use of Sevi- fewer ears than the untreated plots. t y of California, Riverside.
mol (or Sevin and molasses) for
Table 1. Evaluation of insecticides for control of
control of corn earworm is present- corn earworm and R. pod; on sweet corn in Table 2. Evaluation o insecticides for control of corn
f
ly widespread among sweet corn Riverside, Ca.-1974 earworm on sweet corn in Riverside, Ca. -
growers in southern California. 1974
However, the results indicate that Lb. actual Percent Percent
this material may not provide ade- toxicant earworm- aphid- Lb. actual Percent
per infested infested toxicant per eorworm-infested
quate protection when earworm Treatment acre ears ears Treatment acre ears
populations are high. Of the com- ~
pounds tested, only Lorsban pro- Lorsban 1 .o .
35a 2.5 a FMC 33297 .
01 5 a
vided effective control of both the Lannate 0.45 3.0 a 56.0 b RH 218 0.5 15 a
Gardona 1.5 4.5 a 86.5 c RH 218 1 .o 8a
corn earworm and the aphid. Sevimol 3.0 20.0 b 49.5 b uc 49035 1 .o 12 a
T h e experimental compounds, Untreated 78.0c 96.0 c Untreated 75 b
FMC 33297 (a synthetic pyreth-
roid), RH 218 (an organophos- Means in column followed by same letter not Means in columns followed by same letter not
significantly different - Duncan's multiple range test significantly different - Duncan's multiple range test
P10.05 P50.05
Reseurch Briefs for CALIFORNIA AGRICULTURE
HIGH-ENERGY RATIONS cent concentrates appeared to be Imperial Valley. - F. E. Robinson,
optimum. Costs, obviously, would Department of Water Science and
Results of three studies to date in determine the levels chosen. - G. Engineering, Davis.
a continuing project aimed at deter- P. Lofgreen, Department of Animal
mining the effects of dietary treat- Science, Davis, Imperial Valley HEAT-TREATED, VIRUS-FREE
ment on body composition and Field Station. MEYER LEMON CLONES
performance of beef cattle indicate
that maximum performance on a Two heat-treated, virus-free Mey-
high-energy ration is achieved by CATTLE WASTE NITRATE DIS- er lemon clones developed through
cattle grown to 500 lbs. before POSAL the Citrus Variety Improvement
being given the high-energy ration. Program are being compared with
To obtain data for determining A recent Imperial Valley Field four old-line, virus-infected clones
what procedure should be used to Station study of an unlined, liquid- on three rootstocks and as own-
grow calves to 500 Ibs., various cattle-waste digestion pond showed rooted seedlings in a study at the
energy levels were compared. In that soil sealing occurred in 3 South Coast Field Station. So far,
general, the rate of growth was weeks and that the order of magni- evaluation of the heat-treated, vi-
dependent on energy concentration tude of nitrate addition to the rus-free clones for production and
in the ration. Considering the ground water was 0.27 Ibs. per fruit quality in this planting give
growth and efficiency to 500 Ibs. steer per year. The study was every indication that they can suc-
on the growing ration and the conducted as part of a current c e s s f u 11y rep 1ace v i r u s - i n f ect ed
performance on the high energy project at the station which is Meyer lemons.- W. Reuther and E.
ration from 500 Ibs. to finish, a aimed at improving irrigation man- C. Calavan, Department of Plant
growing ration containing 72 per- agement and salinity control in the Science, Riverside.
CALIFORNIA AGRICULTURE, AUGUST, 1975 5
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